Commit 5b438f01 authored Apr 23, 2021 by Andrii Nakryiko Committed by Alexei Starovoitov Apr 23, 2021

bpftool: Dump more info about DATASEC members



Dump succinct information for each member of DATASEC: its kinds and name. This
is extremely helpful to see at a quick glance what is inside each DATASEC of
a given BTF. Without this, one has to jump around BTF data to just find out
the name of a VAR or FUNC. DATASEC's var_secinfo member is special in that
regard because it doesn't itself contain the name of the member, delegating
that to the referenced VAR and FUNC kinds. Other kinds, like
STRUCT/UNION/FUNC/ENUM, encode member names directly and thus are clearly
identifiable in BTF dump.

The new output looks like this:

[35] DATASEC '.bss' size=0 vlen=6
        type_id=8 offset=0 size=4 (VAR 'input_bss1')
        type_id=13 offset=0 size=4 (VAR 'input_bss_weak')
        type_id=16 offset=0 size=4 (VAR 'output_bss1')
        type_id=17 offset=0 size=4 (VAR 'output_data1')
        type_id=18 offset=0 size=4 (VAR 'output_rodata1')
        type_id=20 offset=0 size=8 (VAR 'output_sink1')
[36] DATASEC '.data' size=0 vlen=2
        type_id=9 offset=0 size=4 (VAR 'input_data1')
        type_id=14 offset=0 size=4 (VAR 'input_data_weak')
[37] DATASEC '.kconfig' size=0 vlen=2
        type_id=25 offset=0 size=4 (VAR 'LINUX_KERNEL_VERSION')
        type_id=28 offset=0 size=1 (VAR 'CONFIG_BPF_SYSCALL')
[38] DATASEC '.ksyms' size=0 vlen=1
        type_id=30 offset=0 size=1 (VAR 'bpf_link_fops')
[39] DATASEC '.rodata' size=0 vlen=2
        type_id=12 offset=0 size=4 (VAR 'input_rodata1')
        type_id=15 offset=0 size=4 (VAR 'input_rodata_weak')
[40] DATASEC 'license' size=0 vlen=1
        type_id=24 offset=0 size=4 (VAR 'LICENSE')

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210423181348.1801389-3-andrii@kernel.org

parent 0dd7e456

tools/bpf/bpftool/btf.c

+18 −8

Original line number	Diff line number	Diff line
		@@ -100,26 +100,28 @@ static const char btf_str(const struct btf btf, __u32 off)
		return btf__name_by_offset(btf, off) ? : "(invalid)";
		}

		static int btf_kind_safe(int kind)
		{
		return kind <= BTF_KIND_MAX ? kind : BTF_KIND_UNKN;
		}

		static int dump_btf_type(const struct btf *btf, __u32 id,
		const struct btf_type *t)
		{
		json_writer_t *w = json_wtr;
		int kind, safe_kind;

		kind = BTF_INFO_KIND(t->info);
		safe_kind = kind <= BTF_KIND_MAX ? kind : BTF_KIND_UNKN;
		int kind = btf_kind(t);

		if (json_output) {
		jsonw_start_object(w);
		jsonw_uint_field(w, "id", id);
		jsonw_string_field(w, "kind", btf_kind_str[safe_kind]);
		jsonw_string_field(w, "kind", btf_kind_str[btf_kind_safe(kind)]);
		jsonw_string_field(w, "name", btf_str(btf, t->name_off));
		} else {
		printf("[%u] %s '%s'", id, btf_kind_str[safe_kind],
		printf("[%u] %s '%s'", id, btf_kind_str[btf_kind_safe(kind)],
		btf_str(btf, t->name_off));
		}

		switch (BTF_INFO_KIND(t->info)) {
		switch (kind) {
		case BTF_KIND_INT: {
		__u32 v = (__u32 )(t + 1);
		const char *enc;
		@@ -303,6 +305,7 @@ static int dump_btf_type(const struct btf *btf, __u32 id,
		}
		case BTF_KIND_DATASEC: {
		const struct btf_var_secinfo v = (const void )(t + 1);
		const struct btf_type *vt;
		__u16 vlen = BTF_INFO_VLEN(t->info);
		int i;

		@@ -324,6 +327,13 @@ static int dump_btf_type(const struct btf *btf, __u32 id,
		} else {
		printf("\n\ttype_id=%u offset=%u size=%u",
		v->type, v->offset, v->size);

		if (v->type <= btf__get_nr_types(btf)) {
		vt = btf__type_by_id(btf, v->type);
		printf(" (%s '%s')",
		btf_kind_str[btf_kind_safe(btf_kind(vt))],
		btf_str(btf, vt->name_off));
		}
		}
		}
		if (json_output)